ORA-09945: Unable to initialize the audit trail file

Hi,

one of the instance for our RMAN backup is getting failed due to the following error.

connected to recovery catalog database

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
ORA-09945: Unable to initialize the audit trail file
SVR4 Error: 28: No space left on device

where as in the same DB server we have another couple of oracle instances, which is performing Sucessful RMAN without any error / warnings as well.

what could be the reason for the above error. Pls. provide the solution and revert back need to fix ASAP.

Thanks,

Siva..